Horizontal banding issue
I am having an issue with horizontal banding at regular intervals. I thought it may be over extrusion but having calibrated the filament I still have the issue. 
Speed, extrusion multiplier, and linear advance
The easiest thing to try is simply slowing the print down. Dial speed back 50% using the front knob mid-print. If that improves things, you know you can fix the problem in slicer settings.
Try changing your z-seam position (Print Settings->Layers and perimeters->Advanced->Seam position). If that improves the appearance, you can try calibrating your extrusion multiplier and linear advance settings for that filament to even out flow.
Banding issue
Thanks for the advise. I tried slowing down the print but it didn't seem to make any difference.
I have calibrated the extrusion multiplier, any suggestions on setting for the linear advance?